Automatic telephone and supervisory system.



H F. LUBBERGER. AUTOMATIC TELEPHONE. AN D SUPERVISORY SYSTEM. APPLICATION FILED NOV. 30, I907.

1 1 96,876. Patented Sept 5, 1916.

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F. LUBBERGER.

AUTOMATIC TELEPHONE AND SUPERVISORY SYSTEM.

APPucmpN FIL ED NOV. 30, 1901.

1,1 96,876. Patented Sept. 5,1916.

6 HEETS-SHEET 2.

F. LUBBERGER.

AUTOMATIC TELEPHONE AND SUPERVISORY SYSTEM.

APPLICATION FILED NOV-30,1907.

' F. LUBBERGER.

AUTOMATIC TELEPHONE AND SUPERVISOBY SYSTEM.

APPLICATION FILED NOV. 30; 1907.

,19 7 Patented Sept. 5, 191% 6 SHEETSSHEET 4- F. LUBBERGER. AUTOMATIC TELEPHONEYAND SUPERVISORY SYSTEM.

APPLICATION FILED NOV. 30, 1907.v

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APPLiCATION F|LED NOV- 30, 1907- Li9 $?s Patented Sept. 5,1916.

6SHEETS-SHEET 6.

ATENT OFFICE.

FRITZ LUBBERGER, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC CO, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE AND SUPEBVISORY SYSTEM.

Specification of Letters lfdtenh Patented Sept, 5, 1916.

'Application filed November 30, 1907. Serial No. 404,536.

To all whom it may concern: I,

7 Be it known that I, Fnrrz LUBBERGER, a subject of the Emperor of Germany, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Automatic Telephone and Supervisory Systems, of which the follow ing is a specification.

My invention relates to automatic telephone systems in general, but more particularly to automatic telephone systems in which electrically-propelled and step-bystep automatic switches are employed, such as selectors and connectors, and especially to systems of this kind in which the automatic exchange apparatus is distributed between a main or central station and one or more sub-central or outlying stations.

-The principal object of my invention 1s the provision of improved means for .enabling the attendant at the main or central station to automatically be signaled in case of trouble at any one of the sub-central or outlying stations. 1

It is also an object to provide-an arrangement by which di'fierent kinds of trouble at the sub-central or outlying stations will produce different kinds of signals at the main or central station, whereby the attendant may not only readily locate the station at which the trouble had developed, but may also know immediately the character of such trouble.

Another object is to provide improved means by which the attendant at the main or central station may at will test the apparatus, or certain portions thereof, at the subcentral or outlying stations. e

To the foregoing and other useful ends, my invention consists in matters herelnafter set forth and claimed. 1

In the accompanying drawings Figure 1 shows in a general way the relative location of the different switches employed in the district system in connection with which I have elected to explain my invention. As shown in this figure, the large circles. represent the district or sub-central stations. As shown at the top of the figure'the 2200 subcentral comprises line switches C and connector switches H. At A there are represented the subscribers stations.

at the main central station. v

First and second selectors are provided in the central exchange for trunking and are divided lnto thousand groups. The one-thousand-group switch C, the master switch E for controlling the line'switches of the group of which C is a member; and a battery B, having its positive terminal preferably grounded at G, for operating the apparatus. At the left of the diagram there is shown the sub-central supervisory equipment and apparatus, which is one of the important features of my invention, and with which each sub-central of Fig. 1 is equipped.

In Fig. 3 is shown diagrammatically one of the first-selector switches D and one-of the second-selector switches F, both of the general type of selector disclosed in United States Patent No. 815,321, grante'df March 13, 1906, to Keith, Erickson and Erickson, which, as stated,'are located in the main central office. Also, a battery B is shown which i may be located at the main central station.-

Fig. A shows diagrammatically one of the connector switches H of the general type disclosed in United States Patent No. 815,176, granted March 13, 1906, to Keith, Erickson and Erickson, but modified somewhat to adapt it to common battery work. At C there is shown a line-switch allotted to the line of substation A, which is the vsame as line switch The battery B. is, also shown. It will be understood that with a main central battery," separate leads or conductors will extend to each sub-central; but for convenience I have shown a battery at each sub-central station, aswell .as one Figs. 2, 3 and 4 taken together represent diagrammatically the switching apparatus sis involved in establishing a 'connection b'etween a subscriber of the sub-central #5000, for example, anda subscriber of the #2200 sub-central. Fig. 5 is a diagrammatic view of the line switch C and the master switch E.

Fig.6 is a detail view showing the construction of themaster switch bank 0. Figs. 7, 8, 9, 10,11, 12 and13' are detail each. Thento each group line switches there 1S allotted a group of first-selectors,

usually ten in number, making one-thousand first-selectors in a ten-thousand system.

' Furthermore, the second-selector switches ticu-lar line.

those which may be termed the ser1ous--are are arranged in suitable groups with regard to the first-selector banks, and the connectors are also arranged in suitable groups with regard to the second-selector banks.

Ina-district system it is, "of course, desirable to provide supervisory means whereby the main exchange attendant may be kept informed at all times of the condition .of the "sub-central equipment. As has been shown by practice, there are various troubles which arise at a sub-central station that effect its successful operation'more or less. It

"is desirable, of course, that these troubles be lanown to the main exchange attendant as soon as they occur, in order that he may act accordingly. Some of the troubles which .arise at a sub-central station are of a very serious. character, since they affect all of the subscribers allotted to a sub-central, while others are minor andfaifect only one par- Of the former class-that is,

the following: the blowing of the main fuse; the blowing of the fuse which pro vides the bridge-cut-ofi" relays with battery current; and master switch trouble. The

occurrence of any one of the above mentioned troubles would seriously impair the service of a whole group of subscribers. These serious troubles-are indicated to the main exchange attendant by the glowing of a 1re'd'lamp. The minor troubles-that is,

those which do not afi ect the whole sub-central, but only one line-are as follows: the blowing of a line fuse; and the blowing of a trunk-line fuse. The blowing of either of these fuses affects only one line and is indi-' cated to the main exchange attendant by the glowing of awhite light. Thus, the main exchange attendant is not only informed of the trouble at a sub-central, but is also able to tell whether or not the trouble is serious and demands immediate attention.

The substations may be of any suitable or approved. type. Those in connection with which I have elected to explain my-invene tion comprise, as shown at substation A, a receiver 2, a switch-hook 3 for controlling the substation circuits, -.Which controlling. operations are accomplished through the mediumof any suitable means, such as the I are -,e7r

cam-arms 4i, 5 and 6. As the switch-hook is lowered the cam-arm 5 momentarily presses the release sprii 7, 8 and 9 intd engage ment, whereby the substation line conductors may be grounded simultaneously. When the switch-hook is down the cam-arm 6 maintains a contact between the springs 10 and 11, thereby bridging the ringer 12 in series with the condenser 13 across the line! The substation is provided-with a grounded circuit which is normally broken between the so-called ground springs 14 and 15 by the can1-arm a; but when said springs are together, ground is provided to the ground post 1.6 and to the release spring 7, as is usually the case in telephones of this type. The. said substation comprises the usual transmitter 17, and the induction-coil 18 having the primary winding 19 and secondary .winding' 20. Being an automatic substation it is provided with the usual vertical and rotary impulse springs 21 and 22. For operating the impulse springs 21 and 22 the substation is provided with an impulse wheel 33 that is secured to the shaft 30. This impulse wheel carries on its periphery the so-called-vertical impulse teeth 2% and dial is rotated in one direction, and once when rotated in the opposite direction. The said rotary impulse spring 22 has on its under side a V-shaped member 25 having two'sides c and cl, and there is in addition an auxiliary spring 26 which works in conjunction with the V-shaped member.

As shown more clearly in Fig. 7, the auxiliar 1 spring 26 is provided with a lower curved part 27 having the rear section 6 curving outwardly, as shown in Figs. 7, -8 and 9. The front section 28 of the said member 27 is designed to fall just below the apex of the V-shapcd member 25, so tha? when the rotary impulse tooth 29 is movec in the direction indicated by the arrow in Fig. 8, it will pass onto the curved member 27, thus pressing the rotary impulse spring andeventually the first tooth that meets the lug clears the said lug, as shown in Fig. 10, but not until after the rotary impulse tooth 29 clears the curved. member 27.

the impulse wheel continues to advance in the direction indicated by the arrow in Fig.

10, the succeeding impulse tooth will clear the projection 23, as shown in Fig. 11. Then when the impulse wheel isreleased, first the Vertical impulse spring 21 is carried into engagement with the ground post 16 twice by the vertical teeth previously cleared, as in- (heated in Fig. 12; but as the impulse wheel nears its normal position the rotary impulse tooth 29 passes under the curved member 27 of'the auxiliary spring 26 (Fig. 11), engaging the V-shaped member 25 directly and for a short time only, sending the ordinary impulse to the line through the medium of the rotary impulse spring 22; after which the-said member 27 is cleared, as shown in F ig. 8, as the impulse wheel reaches its normal position. 20

The operations, as thus described, are repeated each time that the dial is turned, and

the number of impulses produced through the medium of the vertical impulse spring are accurately and definitely determined ateach operation of the dial. Said substation as, of course, provided with a dial (not shown) which is secured to the shaft 30, to-

gether with the locking-dog 81. F urthermore, there is a locking cam 32 that--locks the dog 31, while the receiver is on the switch hook, to prevent a rotation of the dial. The said impulse teeth 24 and 29 are so arranged that when the dial is drawn down the rotary impulse spring 22 is pressed. into contact with the ground post 16 while the impulse spring 21 is not carried into contact with the said ground post; but as the dial returns, first the vertical teeth 24 engage the vertical impulse spring 21, and after they have completed their work the rotary impulse tooth 29 operates the rotary scriber may signalafcalled subscriber com-' prises the push-button 38 which, when pressed, carries the spring 39 out of engagement with the contact point 40 and into engagement with the contact point 41, whereby the vertical line conductor 34 1s grounded, The line switch C (Fig. 5) comprises a plunger,42, plunger arm 43, 1311p magnet 44, and switch-release magnet 45, all

. of which are assembled upon a suitable base or frame not shown. The said switch-release magnet is provided with an armature 46 that is plvoted on a pin 47 which rises from the base of the switch. The said armature carries p-ivotally secured on its end a second armature 48 that is controlled by the trip magnet 44, The pin 49 about which the armature 48- moves is carried on the end of the armature 46. The plunger 42 is pivotally secured by the pin 50 to the plunger arm 43, which latter is in turn pivoted to a pin 51 that rises from the switch frame (not shown). i I

The lug 52 may be stamped from the frame and is provided as a stop for the armature 46. Upon the armature 48 is secured the catch 53 which is adapted to nor- 43. provided with a bank of terminals, usually ten in number but only one of which is shown at Q (Fig- 5). is shown twisted from its true position with respect to the swing of the plunger 42, and the bushing 62' is correspondingly turned,

all for the purpose of making the il1u'stra- 'mally engage the end 54 of'the plunger arm 1 Furthermore, the said line switch is" The said terminal Q tion clearer. Thev terminal Q comprises the springs 63 and 64, 65 and 66, 67 and 68, and

69 and 70. These springs are normally disconnected from each other, but are driven into contact in the above-mentioned order when the plunger 42 engages the terminal Q. When the plunger 42 disengages' from' the bank terminal Q the said plunger may take one of two positions in relation to the plunger shaft 60 that is, the plunger may return to locking or sliding engagement with the shaft 60.. When the plunger 42 is in locked engagement with the plunger shaft 60 the notch 61 is in engagement with the flange or web of the shaft 60, and when position shown by the dotted lines in Fig. 5.that is, when the plunger shaft is operated the plunger 42 is "not carried along With the locked plungers, but remains in the dotted position, the plunger shaft sliding upon the edge 59.

The general operation of the switch is as follows: The trip magnet 44 is energized by the preliminary impulse, and the armature 48 is attracted against the magnet cores.

When the armature 48 is attracted the catch 53 slides out of contact with the end 54 of the plunger arm 43, and the said plunger arm 43, owing to the tension of the spring 58, moves about the pin 51 and thrusts the plunger 42 into the bank terminal Q, as shown in Fig. 5; and when the trip magnet again deenergizes, the trip armature 48 falls against the end of the plunger arm 43, as shown.,' V Furthermore, when the line switch operates, and the plunger 42 is thrust into the bank terminal Q, the shaft 60 is advanced one step, as will be explained, to

carry the remainingplungers opposite the 33 115 ,in sliding engagement the hub rests in the next idle trunk-line; The switch is restored when the release magnet 45 becomes energized, whereby the armature 46 is attracted, and accordingly the trip armature 48 is moved upwardly until the catch 53 slides over the end 54; then when the release mag net 45 becomes deenergized the armature 46 returns to normal position and remains at rest against the stop 52, furthermore,

since the plunger arm 43 isnow in engagement with the armature 48, the said plunger arm is also moved about the pin 51, whereby the plunger 42 is moved from the terminal Q. Also, since the plunger shaft has advanced one step, the hub 59 of the plunger 42 comes to rest in the position shown by the dotted line in Fig. 5, in sliding engagement with the plunger shaft and as the said plunger shaft advances each time an idle trunk is seized, the plunger 42 is not advanced, but remains in this position opposite the trunk terminal from which it last disengaged, since the slot 61 is not in engagement with the plunger shaft 60. After all the trunk-lines have been successively seized, the shaft 60 then passes from its last position and moves toward the starting point, picking up the plunger 42 when the web of the said shaft, over which the slot 61 normally rides, arrives at the position at which the plunger 42 was originally releasedfthat is, the plunger passes into locked engagement with the shaft when the slot 61 slips over the web of said shaft. From thence on the plunger 42 is carried in locked engagement by the shaft 60 until it is again released when another call is made. But if, after the plunger is released, and before the shaft 60 returns to pick up said plunger, the switch C is again operated, the plunger 42 again engages the same terminal Q. The bridge-cut-off relay 55 is provided for controlling the springs 56, 57, 56" and 57 and, upon'energizing, operates to shift the spring 56 from the spring 56 to the spring 57. When the spring 56 is thus operated the springs 56 and 57 also disengage.

The master switch E, which may be of any suitable or approved type, is provided for operating the plunger shaft 60 and for controlling certain circuits that will be dis closed hereinafter. It comprises the following details: A motor magnet 71 for operating the ratchet wheel 72, which latter is designed for operating the plunger shaft 60 through the medium of the cam 74, and a differential relay 7 3 for controlling the en'ergizing circuit of the motor magnet 71. The said master switch also has a bank 0 comprising a plurality of individual contact segments a and a common metallic segment .75, as shown in. Fig. 5. The wiper 76 is adapted to remain in constant engagement with the bank 0, and to maintain at measve times, except when the wiper is passing from the extreme left contact 77 to the extreme right contact 7 8, some one of the segments a in electrical connection with the common segment 75. As shown in Fig. 6, the individual segments a are separated from the common segment by the insulating strip 7 9. The spring 80 is provided in order that when the wiper 76 passes to the last contact point '77, then on the next step the wiper is car ried to the contact 78 on the extreme right, and the upper part of. the wiper 76 slides on the guide spring 80, thus preventing the wiper from placing any of the individual segments a: in contact with the common segment 75, as otherwise some interference might be caused with the master switch. The wiper 76 is operated in a step-by-step manner by the ratchet wheel 72, through the medium of the cam member 74 rigidly secured to the said wiper 76 and adapted to successively engage the pins 81, 82, 83 and 84 upon the said ratchet wheel 72. The motor magnet 71 is provided with an armature 85 upon the end of which there is suitably secured a pawl 86. Each time that the said magnet is energized the armature 85 is attracted against the magnet cores, and the pawl 86 engages the next lower tooth on the ratchet wheel 72; then when the magnet deenergizes, the pawl 86 engages the ratchet wheel 72, advancing the latter one step. It will be seen, therefore, that as the ratchet wheel 72 advances in a clockwise direction, the wiper 76 advances step by step from right to left; and when the pin 81, for example, clears the cam 74 the retracting spring 87 restoresthe wiper 76 to its first position at the right of the bank and in engagement with the first segment 78. The said motor magnet is provided with a conple of interrupter springs 88 and 89 that are included, in the energizing circuit of the said motor magnet, which energizing circuit also comprises the springs 90 and 91 controlled by the difierential relay 73. Therefore, Whenever the differential relay is energized the springs 90 and 91 are pressed into contact, and the motor magnet 71 operates step by step as long as the differential relay 7 3 remains energized.- Furthermore, it is assumed that the terminal Q3 of the line switch C is the first terminal of the line switch bank. While in normal looking engagement with the shaft 60 the plun ger 42 is retained in front of said terminal by the plunger shaft 60 whenever the master switch wiper 76. is in engagement with the bank segment 78; but as the motor magnet 71 advances the wiper 76 onto the second segment 92, the said plunger and all l l 1 f springs 63, are also common, and thesprings 70 and 66, like the springs 64, are individual.

For every bank terminal Q there is a trunkline of three conductors 93, 94 and 95 leading to a selector, and there is also a normal trunk-line comprising the conductors 96, 97 and 98 leading to the connector banks. The subscribers line conductors 34 and 35 terminate in the springs 63 and 65 which, as has been stated, are common springs. When the subscriber operates the line switch C and the plunger 42 engages the terminal Q, g

the subscribers line conductors 34 and 35 are extended to the vertical and rotary trunk conductors 93 and 94, thence tothe. switch D.

The mechanical detailsof the first-selector are, in general, well known, involving a vertical magnet 99 and a rotary magnet 100, a release magnet 101 and a private magnet 102. The said private magnet 102,'of course, controls the side switch wipers 103, 104, 105 and 106, the said private magnet also con trolling the circuit of the vertical magnet 99 in the usual manner by means of the springs 107 and 108, but not the circuit of the release magnet, for the release magnet spring is omitted. The movement of the switch shaft and, therefore, of the wipers 109, 110 and 111 is controlled by the vertical magnet 99, and the rotary movement by the rotary magnet 100, the rotary magnet circuit being provided with the usual interrupter springs 112. The operative magnets of the switch are, of course, controlled by ,the subscriber through the medium'of the Vertical and rotary line relays 113 and 114, as is well known. Said relays have under their control the usual springs 115, 116 and 117, and in addition the trunk-release springs 118 and 119, whereby the, said switch. may be released when the side switch wipers are in first or second position. By means of the back-release relay 120 the release of the switch D is brou-gh about after the side switch has passed to third position. Furthermore, the selector switch D is provided with a supervisory relay 121 which, upon.

energizing, operates to close a circuit through the signal lamp 122, whereby the exchange attendant is notified that the trunk-line to which the first-selector is allotted has been seized by a line switch. The supervisory lamp 123 is common to the group of first-selectors of which the selector D is a member, and is provided for indicating to the attendant when a first-selector switch has fully operated and established connection with a second-selector sw tch,

The selector F is also a modified form .of the selector of'the said selector patent. It is of the trunk-release type, in which the line relays 124 and 125 are permanently connectedw ith the side switch contact points,

126 and 127. It is also provided with the vertlcal magnet 128 and the rotary magnet 129, the release magnet 130 and the private -magnet 131. As shown, the :line relays 124 and 125 control they so-called trunk-release springs 132,and 133, the former being connected with the trunk-release conductor and the latter with the release magnet 130. The rotary magnet 129 is provided with the usual interrupter springs 134. Since the selector is of the trunk release type, the back-release relay affords means of releasing the said switch after the side switch passes to third position. s Q H The mechanical details of the selector and connector (Fig. 4), as is well known, are very much the same. For instance, the con nector switch'shaft (not shown), like the selector, carries a set of line wipers 138 and 139 and. a private wiper 140. The connector switch is also controlled by the calling subscriber through the medium of the vertical and rotary line relays 141 and 142. The

vertical line relay 141 directly controls the.

vertical magnet 143 and also the rotary magnet 144. The purpose of the vertical magnet 143 is to give the shaft and shaft wipers a vertical motion and the rotary magnet 144 imparts to the shaft and shaft wipers a r0 tary or circular motion, The rotary line relay 142 controls the private magnet 145 which, under certain conditions, controls in turn the vertical, and rotary magnets 143 and 144, the release magnet 146,-and also the side switch wipers 147, 1.48, 149 and-150. The side switch of the connector, like the side switch of the selector, has a normal or first position, a second position and a third position. The release magnet 146 is also controlled by the vertical and rotary line relays 141'and142'conjointly. By the use of the condensers 151 and 152 the circuit through the connector is divided into .two sections. The connector is provided with a differentially-woundrelay 153 which is composed of the windings 154-and 155. Through the windings of this relay the calling subscribers substation is provided with talking battery current when the primary circuit of the. called substation is bridged across the line. The sub-central stations are equipped said induction-coil. "W1 1en the side switch is in first position, and when the connector shaft is raisedone or morestepafthe induced in the secondary winding 163 of the from the switch-hook and operates the calling device once for each dig ihlin the wellknown manner-that 18, when the dial is rotated for the. first digit a preliminary impulse is transmitted over the rotary line conductor. This preliminary impulse energizes the trip magnet a l, whereby the line switch C is operated to seize an idle trunk-line leading to a first-selector; in returning to normal position for the first digit the dial operates the first-selector switch to establish connection with anidle trunk-line leading to a second-selector switch. It will he understood, of course, that when the dial is turnedtfor each digit a preliminary rotary impulse is transmitte to the rotary line, which impulse, if the selector D or a conhector H is on the line, is received bythe rotary line relay of the switch while the side switch is in first position. This rotary line relay energizes, of course; but since the side switch is in first position, this is without effect, and the switch is not operated until the dial delivers the vertical impulsesj Said preliminary impulse is effective only in operating the line switches. The impulses delivered by the dial for the second digit are received by the second-selector. The impulses for the last two digits are directed toward the connector H which operates to place its shaft wipers in connection with the contacts corresponding to the desired line The preliminary impulse for operating the line switch C, and which occurs when the calling subscriber rotates the dial in a forward direction for the first digit, is caused 2y the rotary impulse spiring 22 being pressed against the ground post 16. As a result of the impulse the trip magnet 47. of the line switch C is energized hya flow of current from ground G to the springs i l and 15, ground post 16, impulse spring 22 to the rotary line conductor 35,

line fuse l' 7l,,conductor 240, cutofi relay springs 56 and 57 to the trip magnet a l, thence through said trip magnet to the conductor 241, springs 242 and 90, springs 88 and 89, through the winding of the motor magnet 71 to the battery lead 199, thence through battery B to ground G. Although this circuit includes the motor magnet 71, this magnet docs not operatively energize, since the magnet 44 is of much higher re sistance thanthe magnet the trip magnet 44: energizes, the armature As soon asl8 is attracted and the plunger 42 is liberated and thrust into the bank terminal Q by the spring 58,. assuming that the plunger 4-2 is opposite the terminal Q; at the time. lli hen the plunger 42 engages the bank terminal I Q an energizing circuit is closed through the motor magnet relay 7 3, which in turn operates to close an energizing circuit through the motor magnet 71. The motor magnet then operates to advance all idle plungers that are in locking engagement with the shaft 60 to a point opposite the next idle bank terminal similar to the terminal. Q. The circuit through the relay 7 3 extends from ground G through the winding 243 of the relay 73, segment 75, wiper arm 76, segment 78, conductor 2%, bank terminal springs and 69, release magnet 41:5, to the battery lead 199,'thence througn battery B to ground G. Although this circuit-includes the release magnet 435 the magnet 45 does-not operatively energize, since the windings of the relay 73 are of a high resistance while the windings of the release magnetis comparatively low. The relay 7 3, upon energizing, operates to place the springs 90 and 91 in contact, whereby a circuit-is completed through the motor ma 5;,- net 71 extending from ground G through the springs 91 and 90, motor magnet springs 88 and 89, through themotor magnet 71 to the battery lead 199, thence through bat-- tery B to ground G. The motor magnet 71, upon energizing, attracts its armature 85,

wvhereby the pawl 86 is driven down and engages the next lower tooth on the ratchet I wheel 72. When the motor magnet 71 deenergizes, the armature 85 returns to normal position, rotating the ratchet wheel 72 one step. 7

When the armature 85 is attracted against the magnet cores, the springs 88 and. 89 disengage, thereby breaking the energizing circuit through the motor magnet. The cam 74, being in engagement with the pin 81, is

operated to advance the plunger shaft SP, and consequently all idle plungers that may be in normal locked position with the shaft 60, one step and opposite another trunk terminal similar to the terminal Q (assuming the next succeeding trunk is idle). Conse quently, the wiper 76 is carried from the contact point 78 (which corresponds to the terminal Q) to the contact point 92, which latter corresponds to the terminal before which the advanced idle plungers are now resting Suppose that nine subscribers have called, and that the master switch has thus been operated nine steps, carrying the wiper 76 to the last contact point 77. Now, when the motor magnet 71 operates for the next step, and when the tenth subscriber calls, the wiper 76 passes back and drops into engagement with the contact point 78, as already explained; It the first trunk is stilllousy the wiper 76 finds battery current on the contact 78, and an energizing circuit is established through the differential relay 73, which 1n turn operates to close an energizing circuit throughthe motor magnet 71. The

current through the said relay 73 flows from its armature, the differential relay. springs net springs 88 and 89, motor magn 90 and 91 are pressed into contact, thereby closing an energizing circuit for the motor magnet 71 from ground Gr throughthe said springs 91 and 90, through the motor marget 1 thence to the battery lead 199 and througli battery B to ground G. The motor magnet then operates, as previouslyexplained, to

rotate the ratchet wheel 72 one step for advancing the plunger shaft 60 one step, and

the master switch bank wiper 76 one stepalso' and into engagement with the second segment 92. The plunger shaft 60, when thus advanced one step, carries all idle plungers that are in engagement with the said shaft to a point oppositethe next bank terminal, as previously explained. If there should still be a guarding potential at the bank segment 92 of the master switch bank the differential relay 73 will remain energized, whereby the energizing circuit through the motor magnet 71 is again completed when the motor magnet springs 88 and 89 again engage, and as a result the motor magnet 71 is again operated, whereby the plunger shaft 60 and the master switch wiper 76 are advanced another step. This process continues as long as the wiper 76 finds segments with guarding potentials. -As soon as an idle segment is found, however, the energizing circuit through the differential relay 73 is broken, at which time the said relay in turn breaks the energizing circuitfor the motor magnet 71 until the next subscriber makes a call. At the instantthat the plunger 42 enters the said bank terminal Q the following springs are ressed into contact: 63 and 64, 65 and 66, 6 and 68, and 69 and 70. The. engagement of the springs 67 and 68 closes a circuit through the cut-off relay extending from ground G through the springs 68 and 67, conductor 245, relay 55 to the conductor 180, fuse 168, bus bar 178, thence through battery B to ground G. The said relay, upon energizing, breaks the contact between the springs 56, 56 and 57,

I whereby the vertical and rotary line conductors 34and 35 become disconnected from the trip magnet 44. The cut-off relay, upon energlzing, places the springs 56 and 57 in contact, which connects the 'subscribers verticalline conductor 34 with the normal conductor 96.

The engagement of the bank, springs 67 and 68 establishes a guarding potential by I way of the normal conductor 98 to the con nector private bank contacts corresponding to the line that terminates in the line switch C, to prevent any subscriber from calling the said line after the callingsubscriber at normal conductor 98. Also, the closure of I connection between the springs 69 and 70 establishes a guarding potential at the mas ter'switch bank contact 78, over the following circuit: from battery B to the battery lead 199, thence through the release magnet 45 and springs 69 and 70 over the conductor 244 to the said contact point 78. This guard ing potential protects the seized trunk conductors 93,94 and 95 from being seized by other plungers, as already explained. Furthermore, the engagement of the bank springs69 and 70 also closes an energizing circuit through the supervisory relay 121 of the first-selector switch (Fig. 3). This circuit extends from ground G at the selector switch through the side switch wiper 105,

conductor 254, through the winding of the relay 121, conductor 255, through the relay 256, heat coil 173, conductor 95, bank springs 70 and 69, release magnet 45 to the battery lead 199, thencethrough battery B to ground G. Although this circuit includes the magnet 45 and the relay 256, the said magnet and relay do not operatively energize, since the winding of the supervisory relay 121 is of comparatively high resistance. The re? lay 121, upon energizing, places the springs 257 and258 in contact, thus closing a circuit through the signal lamp 122 from-ground G through the said springs and lamp 122 to the battery lead 245, thence through battery B to ground G. The glowing of this lamp indicates to'the exchange attendant that the relay 121 de'e'nergizing and in turn breaking,

the circuit for the lamp 122. The closure of connection between the springs 63 and 64 extends the calling subscribers vertical line conductor 34 to the vertical trunk conductor 93 and to the side switch wiper 103 of the first-selector D. The closure of contact befirst-selector switch D has been seizedby a line switch at the sub-central.

tween the springs 65 and 66 in a similar flow of current from thesubstation ground G through the springs 14 and 15, to the ground post 16, thence through the spring 21 to the vertical line conductor 34-, line fuse 172, line switch bank springs 63 and 64, vertical trunk conductor 93, side switch wiper 103 of the selector 1), vertical line relay 113 to the battery lead 24-5, thence through battery B to ground G Each time that the vertical line relay 113 energizes, the line relay spring 115 is pressed onto the ground spring 116. The vertical magnet 99 is thereby energized, and the wipers 109, 110 and 111 of the selector D are raised to the second level and brought opposite the first contact of said level. The energizing circuit for the said vertical magnet 99 extends from ground G througl'i the springs 116 and 115, private springs 10'? and 108 to the vertical magnet 99, thence to the battery lead 2 15, and through battery B to ground G. Following the vertical impulses the rotary impulse spring 22 is then pressed onto the ground post 16, grounding the rotary line conductor 35 and, therefore, energizing the rotary line relay 114 of the selector 1);

The energizing current passes from ground G to the rotary line conductor 35, thence it flows through the line switch bank springs and 66, rotary trunk conductor 9%, side switch wiper 104 of the selector D to the rotary line relay 114C, to the battery lead 24:5, and through-battery B to ground G. The rotary line relay, upon energizing, presses the line. relay spring 117 onto the ground spring 116, thereby establishing a circuit, through the private magnet 102 from ground through the springs 116 and 117 to the private magnet 102, and through the said magnet to the battery lead 2 15, -tl1ence through battery Bto ground G. The private magnet, upon. energizing and de'einergizing, permits the selector side switch to pass from first to second position, permit-' ting the side switch wipers 105 and 106 to engage the contact points 216 and 2417, respectively. The closure of connection between the side switch wiper 105 and the contact point 246 sets up an energizing'circuit for the rotary magnet from ground G through the side switch wiper 105, contact point 246, interrupter springs 112, rotary magnet 100 to the battery lead 245, and. then through battery B to ground G. The

the private wiper 111 engages the firstgroundcd private bank contact point, the private magnet 102 energizes again, loching the side switch in second position, The

energizing circuit for said. private magnet extends fronithe grounded terminal o1 battery through an occupying switch(not shown) to the private wiper 111, thence through the back-release relay 120 to the side switch wiper 100, contact point 245?,

. privateunagnet 102, thence through said magnet to the battery lead 245, and through.

battery B to ground G. lhe private magnet 102, upon. thus becoming energized, locks the sides-witch wiper in. engage incnt withthe contact'point 2%, whereby a the rotary magnet 100 will be energized step by step until the wipers are carried be yond the last busytrunh-line. At the in stant that the private leaves the last busy contact point the energizing circuit through the private in 1st 102 is destroyed, and as result the selector side switch passes to third. position. llihovn ever, there are no busy trunk-lines, the retary magnet 100 releases the side switch to "third position as soon as the wipers are carried into engagement with. the trunlnline,

As soon as the side switch passes to third positidn, as stated, the suhscribefs line con ductors 3 1 and 35 are extended to coir ductors 2418 and 249' which, in this case, is assumed lead to the second-selector switch 13. The extension of the line occurs, lot course,

as soon as the side switch wipers 103 and 10 1- engage the contact points 251 and 252, respectively. Not only is the subscribers line thus extended, but a guaringpotential is established. at the private wiper111, when the side switch wiper 106- passes onto the ground contact point253, for protecting the seizeo. trunk-line from interference by other calling subscribers. This pot-en tial is established @frornground G to the contact point 253, thence through the side switch Wiper 106, and through the back-re lease relay to the private wiper 111. it

will be seen that the energizing circuit for. the rotary magnet 100, to which reference has already been made, destroyedwhen the idle trunk-line is seized-that is, when the grounded side switch wiper 105 leaves the contact point 246. When the side switch wiper 105 passes to third position. and en the conta c point 259, a circuit is rec closed through the lamp 123 which is alotted to the group of selector switches of which selector D is a member. The circuit through the said lamp extends from ground Gr through the side switch wiper 105, contact point 259, through the lamp 123 to the battery lead 245, thence through battery 'B to ground G. The glowing of this lamp indicates to the attendant that a selector switch has operated and seized a trunk-line leading to a second-selector switch. As shown in Fig. 3, the lamp 123' is also connected to the side switch wiper 105 which is the side switch wiper of another first-selector and corresponds to the wiper 105 of the switch D. In a similar manner the lamp 123 is common to each first-selector of the group of which the selector D is a member, and when caused to glow indicates that one or more'of the first-selectors to which it is allotted has operated and seized a trunk-line leading to a second-selector switch.

The second digit of the number called being 2, the calling subscriber again operates his dial accordingly, as a result grounding the vertical line conductor 34 when the spring 21 meets the ground post 16. The.

vertical line relay 124 of the switch F is, therefore, energized twice by a flow of current from the substation ground G3 to the vertical line conductor 34, thence through the line switch bank springs 63 and 64 to the vertical trunk conductor 93, thence to the side switch wiper 103 of the selector D, contact point 251, vertical line wiper 109, vertical trunk conductor 248,-side switch Wiper 259, vertical line relay 124 to the battery lead 245, thence through battery B to ground G. When the vertical line conductor 34 is grounded for the second digit the vertical line relay 124 operates to close a.

circuit through the vertical magnet 128,

I. which magnet operates to carry the shaft wipers step by step to a point opposite the bank terminals of the second level, as explained in connection with the selector D. When the rotary line conductor 35 is grounded, after the vertical impulses, the rotary line relay 125 is energized, whereby an energizing circuit is established through the private magnet 131, which in turn operates to release the side switch, as described in connection with the selector D. After the switch F comes to rest the shaft Wipers 136 and 137 are in engagement with the trunk conductors 260 and 261, respectively, which lead to the connector switch H (Fig. 4). The private wiper 262 establishes a protecting potential at the contact 263 for guarding the seized trunk-line. The grounding of the line conductors 34 and'35 for the last two digits affects the connector by opcircuits.

relay 141 is energized by a flow of current from the substation ground G vertical impulse spring 21 to the vertical line conductor 34, bank springs 63 and 64, trunk conductor 93, side switch wiper 103, shaft I ,of the differential relay 153 to the battery lead 264, thence through battery B to ground G. The winding 154 of the relay 153 being included in this circuit, the said relay energizes, but its operation at this particular time is Without-effect.

Each time that the vertical line relay 141 operates for the third digit the vertical magnet 143 operatively energizes to carry the shaft wipers 138, 139 and 140 in a vertical direction one step at a time until said wipers are carried two steps and thus brought opposite a level in which are located the terminals of the line #2220. The circuit through the .vertical magnet ,143 extends from ground G through the springs 265 and 266, private magnet springs 267 and 268, side switch wiper 149, vertical magnet 143 to the battery lead 264, and through battery B to ground G. When the rotary line conductor 35 is grounded, following the grounding of the vertical line conductor,

the connector rotary line relay 142 becomes energized through a circuit extending from the substation ground G through the rotary impulse spring 22, rotary line conductor 35, bank springs 65 and 66, conductor 94, side switch wiper 104, shaft wiper 110, conductor 249, side switch wiper 269, shaft wiper 137, conductor 261, rotary line relay '142, winding 155 of the differential relay 153, through the springs 270 and 271 to the battery lead 264, thence through battery B to ground G. The winding 155 of the differential relay 153 being included in this circuit, as is the winding 154 in the vertical line relay circuit, the said relay 153 energizes, but with no effect. The rotary line relay 142, upon energizing, operates to close an energizing circuit through the private magnet 145, which latter in turn operates to release the side switch from first to second position. The'energizing circuit through the private 1nagnet 145 extends from ground Gr through the springs 265 and 272, through the private magnet 145, springs 270and 271 to the battery lead 264, and through battery B to ground G.

, For the last digit the subscriber operates the dial as previously described, grounding the vertical line conductor 34 ten times and the rotary line conductor 35 once. The connector vertical and rotary line relays 141 and 142are operated over previously traced However, when the vertical line relay operates, a circuit is closed through the rotary magnet 144 instead of through the vertical magnet-143, since the side switch wiper 149 is now in second position. Each time that the rotary magnet is energized the shaft wipers 138, 139 and 140 are rotated one step at a time until the said wipers are carried into engagement with the normal of the desired substation. The rotary line relay 142, upon energizing, completes an ens ergizing circuit through the private magnet 145, which latter nowoperates with one of two results, namely the release of the side switch from second to third position, or the so-ca-lled busy-release of the connector. It will be assumed that the former result occurs, and that the side switch passes to third position, whereby the side switch wipers 147 and 148' are placed in connection with the shaft wipers 138 and 139, respectively. Furthermore, when the side switch passes to third position a guarding potential is established for protecting the called line. This guarding potential extends from ground Gr through the side switch wiper 150, cone ductor 276 to the private wiper 140 which engages the private contact of the called line. Furthermore, when the side switch wiperl50 passes to third position ah energizing circuit is closed through the-bridgecut-off relay 277 of the line switch C. This circuit extends from ground G through the side switch wiper 150, shaft wiper 140, conductor 275, through the winding of the bridge-c'ut-ofi relay 277 to the battery lead, thence through battery B to ground G. This relay, upon energizing, operates to carry the spring 278 out of en gagement with the spring 279 and into' engagement with the spring 280, and the springs 279 and 281 disengage. When the springs 278 and 280 engage, the normal conductor 273 is placed in contact with the subscribers. line, conductor; 2 2; The disengagement ofthe. springs 279 and 281 disconnects the substation rotary line conductor 283 from the trip magnet 284 of the line switch C In orderto signal, the subscriber at substation A presses the signaling button 38, whereby the vertical line conductor 34 isgrounded, and the connector vertical line relay 141 and the differential relay 153 become energized. as before.

It will be remembered that the side switch has passed from second to third position, and that the side switch wiper 149 is in engagement with the contact point 285, thereby placing the vertical line relay 141 in control of the ringer relay 157 in the same manner in which the rotary magnet 144 came under the control of the vertical line relay when. the side switch passed from first to second position. Therefore, when the vertical line relay presses thesprings 266 and 265" into contact the ringer relay .157'is enerspring 289 to the spring 290, and the spring 291 is shifted into engagement with the spring 292. This results in bridging the terminals of the ringer generator K across the called subscribers line. 'A signaling current is, therefore, sent from the generator K to the ringer relay springs 292 and 291, side switch wiper 147, shaft wiper 138, normal conductor 273, bridge-cut-olf relay springs 280'and 278, vertical line conductor 282, condenser 293, ringer 294, springs 295 and 296 to the rotary line conductor 283, rotary normal conductor 274, shaft wiper 139, side switch wiper 148, ringer relay springs 288 and 290 back to the generator K As soon as the calling subscriber ceases to press the signaling button 38 the ringer relay 157 becomes deenergized, and the springs 288 and 291 assume their normal position. In response'to the signal the subscriber at substation #2220 removes the receiver 297 from the switch-hook 298, whereby the switch-hook rises and permits the springs 299 and 300 to engage, and the springs 295 and 296 to disengage, thereby removing the ringer 294 from across his line. The engagement of the springs 299 and 300 closes a series energizing circuit through both windings of the relay 156 at the connector H, which circuit extends from ground G to the side switch wiper 150, winding 159 of the relay 156, springs 289 and 288, side switch wiper 148, shaft wiper 139, rotary normal conductor 274, rotary line conductor 283, primary winding 301, transmitter 302, through the signaling device of the called substation, springs 299 and 300, verticalline conductor 282, normal conductor 273, shaft wiper 138, side switch wiper 147, through the winding 158 of the relay 156, springs 303 and 287 to the battery lead 264, thence through battery 13 to ground G. The relay 156, upon energi za' tion, operates to shift the spring 270 from the spring 271 (which latter is connected to the battery lead 264) to the spring 304, which latter is in turn connected with ground. The reversal of the polarity of the spring 270 sets up a circuit which provides the calling substation with battery current for talking purposes. Thiscircuit may be traced from ground G to the side switch wiper 150, through the springs 304 and 270, winding 155 of the differential relay 153,rotary line relay142,conductors261,

- that the said relay does not operatively energize. The vertical and rotary line relays 141 and 142 being included in the above circuit operatively energize and place the springs 265,266 and 272 in contact, and the release springs 305 and 306 are also brought into contac't; but the simultaneous action of these relays 'at this particular time is without effect, since there are no energizing circuits established thereby. The two substa- ,-tions A and A being thus provided with battery current for talking purposes, conversation may be carried on over the-circuit shown by the heavy line conductors in Fi s. 9, 3 and 4. V

The-release of the switching apparatus is brought about when the-calling subscriber restores the receiver 2 to the switch-hook 3, thereby pressing the release springs 7, 8 and 9 into engagement for a moment. The contact of the saidwrelease springs grounds the vertical and rotary line conductors 34 and 35 simultaneously from ground G3 to the release spring 7, thence through the springs 8 and 9 to the Vertical and rotary line conductors. The grounding of the rotary line conductor "35 produces a short-circuiting of the rotary line relay 142, in series 'with the winding 155 of the differential relay 153, said. circuit extending from ground G at the connector to the side switch wiper 150, springs 304 and v270, winding 155 of the differential relay 153, rotary line relay 142 to the trunk conductors 261, 249 and 94,

bank springs 66 and to the'rotary line .conductor 35, release springs 9., 8 and 7 to the substation ground G Therefore, since the winding 154 of the differential relay 153 alonecarries current, the said relay becomes energized and attracts its armature, which shifts the spring 287 out of contact with the spring 303 into contact with the spring 286; The disengagement of the springs 287 and 303 destroys the energizing circuit through the relay 156, and the spring 270 passes out of engagement with the spring I 304- and into engagement with the spring 271, which removes the said short-circuit of the rotary line relay 142 and winding 155, and establishes an energizing circuit instead from the substation ground G through the release springs 7 8 and 9 to the rotary line conductor 35, then to the rotary line re-,

lay 142, as previously traced, winding 155 of the differential relay 153, through the springs 270' and 271 to the battery 'lead- 264, thence through battery B to ground G.

I The rotary relay 142 now operates, and the springs 305 and 306 come into contact whereby. an energizing circuit is established through the release magnet 146 of'the connector H and the release relay 135 of the selector F. However, the current now in passmg, as "above stated, through the winding 155- aids-the winding 154 in maintaining the springs 287 and 286 in contact. The energizing circuit through the release relay 135 and release magnet 146 extends from ground Gr at the selector F to the side switch wiper 307, release relay 135, shaft wiper 262, con ductor 308, trunk-release springs 305 and 306, release magnet 146, springs 286 and 287 to the battery lead 264, and through battery- 1 B to ground G. When the connector release magnet 146 is thus supplied with current itenergizes, and as a result the switch shaft and side switch are restored to normal posi-' tion, thus breaking theconnection between the connector switch shaft wipers 138,139

and 140 and the normal conductors 273, 274 and 275. The back-release relay 135 being in the same circuit with the release magnet energizes simultaneously with the latter and operates to close an energizing circuit through the selector release magnet 130, in series with the release rclay.120 of the selector D, by pressing the back-releasein contact, which springs close a circuitthrough the releasing relay 256 (Fig. 2). This circuit extends from ground G through the springs 313 and 314 to the trunk-release conductor 255, through the relay 256 (Fig. 2), fuse coil 17.3, winding of the release magnet 45 to the battery lead 199, thence through battery B to ground G. When the ground to the line conductors 34 and 35 is interrupted-all the magnets involved in the release are deenergized and all of the switches are fully restored. If the called line #2220 is busy at the time that the calling subscriber #5000 attempts to establish connection, the connector H is released by the last impulse to the rotary line connector 35, as follows: The said impulse energizes the rotary line relay 142 of the connector H, which relay in turn energizes the ,privatemagnet 145, pressing the private springs 318 and319 into contact at terthe private wiper 140 has been carried onto the grounded private bank contact.

7 it is understood, of course, that when ever the line #2226 is busy the connector private bank contacts connected with "he private normal 275 are all connected to ground. I Therefore, since the connector side switch is in second position when the private magnet springs 318 and 319 are brought into contact, an energizing circuit is established through the release magnet 146 from the said grounded private bank contact to the private wiper 1 10, thence to the side switch wiper 150 (which is in second position) to the private magnet springs 319 and 318, to the release magnet 146, through the springs 286 and 287 to the battery lead 261, thence through battery B to ground G. The connector switch shaft and side switch are thus released and connection is not established with the called line. Now, when the calling subscriber presses the signaling button, the vertical line relay 1411 becomes energized and operates to close circuit through the Vertical magnet 1 13. The vertical magnet operates to carry tie switch shaft vertically, whereby the oil-normal springs 164 and 165 engage to permit the busy-signaling current to pass to the calling subscriber in the usual manner. Of course, when the subscriber hangs up his receiver after receiving the busy-signal, he grounds the line relays 14:1 and 142 of the connector H, as already explained, producing the release of the switching apparatus as formerly.

In the preceding it has been shown how the sub-central main office switch operates in establishing a connection. it will. now be pointed out how apparatus operates to indicate to the main exchange attendant the various troubles-' that is, serious troubles, such as, first, the blowing oi the main fuse 186 when. the whole sub-central will be deprived of battery current, thus rendering all of the subscribers substations of this sub-central inoperative;-

second, the fuse 168 in the bridge-entail circuit may blow. It will be understood that 1n a sub-central the group of bridge-cut-oil relays 55 (Fig. 2),101' example, will be supplied with battery current from the same fuse 168; another group, if it is desired to subdivide the line switches in one subexchange, may be in the same manner supplied with current from a second fuse 169. Hence, when any bridge-cutoii fuse blows, a group of bridge-cu't-oil' relays is deprived of battery current and the lines allotted there to are rendered inoperative; third, the master switch E may fail to operate, and all of the subscribers line switches which. are operated by the master switch E will remain opposite the same trunk-line, seizing the same trunkdine to the main exchange. Or, iinor troubles, such as, first, the blowing of the fuse 171 or the fuse 172 in a suhscriber s line (Fig, 2)", second, the blowing oi? the the suh-central supervisoryfuse 173 in the private trunlr. conductor of a trunk-line connecting a sub-central with the main exchange may blow and open the said conductor, thereby preventing the release oi: any line switchwhich might seize this pan tic'ular line. I

The central office apparatus which oper ates in connection with the aforesaid subcentral supervisory equipment comprises the two relays 175 and. 176 which are connected.

-while the other relay remains energized.

For example, when a positive or ground potential is presented on the conductor 177,

then the relay 176 is short-circuited and,

therefore, deenergized with the above-noted result, while the circuit through the relay 17 5 is maintained by the ground upon the conductor 17?. li a negative or main battery potential appears, the relay 175 becomes short-circuited, deenergizing and permitting its springs to engage, thus closing the circuit controlled thereby, while a new circuit is established through the relay 176 by the negative potential at the conductor 177.

As shown in Fig. '2, the negative terminal of the battery 3 is connected with the busbar 178, through the fuse 1 66, and the positive terminal is connected with the busbar 179. From these two busbars taps or conductors lead to the various substation apparatus. As shown, the bridge-cutoff relay 55 is connected. with the main battery busbar 1???? over theconductor 180 through the fuse 1138. Through the-fuses 181 and 182 battery current may be supplied to any other apparatus. As shown in Fig. 2, the relay 183 is normally energized, since it is bridged directly across the terminals of the battery B, the circuit extending from battery B through the fuse 166 to the busbar 178, conductor 184, through the springs 185 and 186, through the relay 183, conductor 187 to the ground busbar 1Y9, thence to ground G. When the main fuse 1.66 blows, then this energizing circuit through the relay 183 becomes broken, and said relay permits the spring 188 to pass out of engagement with the spring 189 and into engagement with the spring 190; also, the spring 191 cs into engagement with the spring 192. When the spring 188 engages the spr 19C ground potential is established on 2 conductor 177, as follows: 11 cm its ground G to the busbar 179 over the conductor 193, through the springs 190 and 188 to the conductor 17 7 As previously explained, the conductor 177 extends from the sub-central station to the main central station, hence the relay 176 becomes short-circuited and deenergizes, permitting the springs 194 and 195 to engage, whereby a local circuit is closed through the red lamp 17 0 in multiple with the ringer 196 and in series with the ringer generator 167. The main central attendant is thereby given both an audible and visual signal, indicating that one of the serious troubles previously mentioned has occurred at the sub-central. Furthermore,

tained in this energized position, as shown.

Suppose a case of master switch trouble to be:

7 as follows: The'master switch relay 73 energizes and places the springs 90 and 91 into contact, thereby in turn closing an energizing circuit'through the master switch motor magnet 71. This circuit extends from ground G through the springs 91 and 90,

motor magnet springs 88 and 89, winding of the motor magnet 71 to the battery lead 199,

, thence through the busbar 178, and through 4 springs engage, a ground potential is placed battery B to ground G. The motor-magnet energizes and attracts. its armature 85, whereby the pawl 86 engages the next lower tooth, but for some reason the armature 85 sticks or remains in its operated position. When the springs 88 and 89 disengage a circuit is closed through the relay 200, since the said relay is bridged across the springs 88 and 89. The relay 200 now energizes and places the springs 201, 202 and 203 .in contact, whereby a circuit is closed through the lamp 204 extending from ground G to the busbar 17 9, conductor 205, through the springs 203, 202 and 201, through the lamp 204 to the main battery busbar 178, thence through battery B to ground G. The glowing of this lamp'indicates to the sub-central attendant that the master switch remains in an operated position. Also, when the said upon the conductor 177 extending from ground G through the conductor 205, springs 203 and 202 to the conductor 177 whereby the'main central signal relay 176 .isagain short-circuited and the main central ofliceattendant is again given a red signal, as be- When the springs fore. When the master switch is operating normally an energizing circuit is momentarily closed through therelay 200 when the springs 88 and 89 separate for each'step of the motor magnet 71. Hence, the red signal lamp at the main central office flashes each time that the motor magnet operates the ratchet'wheel 72 one step. The momentary flashing of the red signal lamp in this man-.

ner indicates to the main exchange attendant that the'master switch is operating normally.

Suppose again that the fuse 168 which normally short-circuits the relay 206, and

which feeds battery to the bridge-cut-olf relays, blows; in that event an energizing circuit is established through the signal relay 206. The relay. 206 then energizes, whereby the springs 207 and 208 are placed in contact, thus closing a series circuit including the relay 209 and lamp 210. This circuit extends from ground G through the busbar 179, conductor 211, through the relay 209, lamp 210, springs 208 and 207 to the main battery busbar 17 8, thence to battery B and to ground G. The glowing of the lamp 210 at the sub-central indicates thatthe fuse 168 fuse 168 is restored the energizing circuit-- through the relay 206 is broken and the relay.

returns to normal position, breaking the energizing circuit through the relay 209, which also returns to normal position, permitting thesprings 185 and 186 to engage, whereby the normal circuit through therelay 183 is again established and this latter relay is in turn restored to its normal energized condition.

In the preceding it hasbe'en shown how the main central attendant is signaled by'the red light 170 when any one of thethree serious troubles appears at the sub-central, and it will now be pointed out how thelminor troubles are signaled to the main exchange attendant. Suppose that the line fuse becomes blown, either by lightning or by accidental ground upon the line conductor 35, or for any reason.- When the fuse 171 blows, the springs; 212'and 213 engage and close 'anenergizing circuitgthrough the lamp 214 in series with the relay 215: Thiscircuit 1 extends from ground'G through the conductor -216,'through the springs 213 and 212,

lamp 214, through the relay 215 to-themain battery busba'r 17 8, thence through. battery B to ground G. The-glowing of the lamp 214 indicates to the sub-central attendant that a heat coil of the group of which'171 is heat coil a member has blown. The relay 215, upon energizing, places the springs 217 and 2-18 in contact, whereby a negative potential is placed upon the line'conductor 17 7 since theresistance of the winding of the relay 215 through the relay 176 which is connected with ground. The relay 175, upon being short-circuited, denergizes and permits the springs 219 and 220 to engage, whereby a circuit is closed through the ringer 221 in multiple with the white signal lamp 176% and in series with the ringer-generator 222. The main central ofiice attendant is thus given an audible and visual signal indicating that onepf the minor troubles has occurred at the sub-central. When the heat coil l'Zl is re stored the circuit through the lamp 21d and. the relay 215 is broken, thus restoring the sub-central apparatus and central oilice re- 12.}? 175 to normal condition. When the line fuse 172 blows an ener 'izin circuit is established through the relay 2.15 in series with the lamp 21% by the engagement of the springs 223 and 224. Also, "when the heat coil 173, which is placed in the trunlere lease circuit,blows, then the springs 225 and 1 226 engage, thus closing an energizing circuit through the relay 22'? extending from ground G through the relay 22?, springs 225 and 226, through the bank springs 70 and 69, winding of the release magnet 45 to the main battery busbar 178, thence through battery B to ground. Gr. It will be seen that the '-release. magnet 1-5 is also included in this circuit; but since the winding of this magnet is comparatively low said magnet does not energize, but the relay 227 operates to place the springs 228 and 229 in contact, whereby a series circuit is closed extending from ground G through the springs 228 and 229, lamp 230, conductor 2231, relay to the main battery busbar 178, thence through battery B to ground The glowing of the lamp 230 indicates to the sub central attendant that the heat coil 1'33 has operated. Furthermore, the relay 22'? may be made, common to'a roup of heat coils of which the 1%3 is a member, and the glowing of the lamp 230 would indicate the group. The relay 215, being included in the above circuit, energizes and places the springs 217 and 218 in contact, whereby the negative potential is placed upon: the conductor 177 in the manner previously explained, and the main exchange. attendant is in turn signaled, as before special line 232-25, connected to The sub-central (Fig. 2) may be provided wi th a line, across the conductors 232 and 233 ofc which there is bridged the rela 234 in series with the condenser 235. New, ii the main exchange attendant desires to test the substation ringer generator, similar to the ringer generator K, allotted to the subcentral of which sub-central substation A (Fig. 4) a member, the main exchange attendant then callsthe number allotted to this line, just as he would call any other line and the same connector switch (connector switch l-l, Fig.4, for example) is operated to bridge the ringer generator across the terminals 232 and. 233 (Fig. 2); and an ener- -7 11g; circuit is also established through the relay 2 34 in series with the condenser 2-35, prtwiding the ringer generator is operating. llhc relay 234 energizes and. places the springs 23 8 and 237 in contact, whereby the energizing circuit is closed through the relay 215 in series with the signal lamp 238. This circuit extends from ground G through the conductor 239, springs 236 and 23?, through the lamp 2238, relay 215, main battery busbar 17S, thence through battery B to ground G. The relay 215 now operates to place the sprin 21'4" and 218 in contact, with the viously explained. results. By operating his signaling button. the exchange attendant causes the lamp i to flash and thus show that the ringer generator at the sub-central is operating. M the rii'iger generator at the sub-central is 1': ct operating, then when this test is made the signal lamp ll' l will not flash.

Fig. at shows the manner in which the the bank contacts of the subcentral connector switches. It is to be understood, of course, that the line 232- -283 in each suhcejutral is connected to the bank contacts of connectors in its own subcentral only.

I therefore provide a .ystern oi supervision and testing by which the main exchange is automatically kept informed. of certain kinds of trouble'as soon as they make their appearance; also, to how promptly a sub excha e attendant attends to cases of trouble, ii there is attendant at the sub-e2:- change, and if not, someone may be sent to look up the trouble and remedy same. 1 also provide means for testing the conductors of the ringer and the master switch at any instant.

From the foregoing it will be seen that 1'. provide a telephone system in which provision is made for automatically reporting trouble, to the central station operator or attendant. Furthermore, the operator or attendant may know immediately whether the trouble is of one character or another.

If the trouble is of a general nature, such as would he likely to put an entire sul central statwnout of service, then the automatic lilo 

